Lifting hook assembly



R. T. FLORA, JR

LIFTING HOOK ASSEMBLY Filed July 30, 1955 United States Patent ()flice 3,306,646 Patented Feb. 28, 1967 3,306,646 LIFTING HOOK ASSEMBLY Russell T. Flora, Jrz, Tipp City, Ohio, assignor to The Flexicore Company, Inc, Dayton, Ohio, a corporation of New York Filed July 30 1965, Ser. No. 475,930 3 Claims. (Cl. 294-2) This invention relates to a lifting hook assembly and, more particularly, to a lifting hook assembly for use on long casting forms for concrete slabs.

The casting forms to be handled by the lifting hook assembly are disclosed in prior Patents No. 3,142,106 and No. 3,061,904, and other patents referred to therein. The casting forms generally have a length of as much as 60 feet and may have a range of widths from about 18 inches to about 3 feet. It is understood that the range is given by way of example only. Each casting form has channels along the width thereof.

As disclosed in the above identified patents, the lower flange of each channel is usually used for stripping a casting form. The top flanges are generally used for handling a casting form other than during stripping.

Due to the fact that casting forms are used in various widths, it is desirable to provide suitable means for engaging the top flanges of a casting form for the purpose of lifting the form. It is natural to provide pivoted hook means terminating in claws for engaging the casting form flanges in connection with such lifting operation. However, certain problems have arisen in connection with such hook means as hereinafter set forth. One such problem involves the range of widths of casting forms to be handled. An additional problem relates to the slope of the inside surface of the top flange. The direction of slope makes it difficult for claws to remain engaged in certain hook positions unless special provisions are made for retaining the claws in gripping position. An additional problem relates to the desirability of having the hooks and claws in an inoperative position when a casting is raised clear of the casting form. This latter operation involves the use of vacuum pads which engage the top free surf-ace of a casting for the purpose of lifting the casting up from the casing form during stripping. When thus elevating the casting, it is necessary that the flange engaging hooks be above the slab top face to permit side by side slab placement.

A further difliculty which has been encountered in the practical manufacture and use of casting form hook assemblies relates to the question of tolerances. The dimensions of casting forms and casting form flanges involve tolerances of the order of about A of an inch. In addition, the manufacture of such casting form hook assemblies in itself involves tolerances of the order of about A of an inch. The net result is that a substantial possible accumulation of tolerances has usually been found to impair the reliability of operation of a hook assembly for engaging a casting form along the flanges.

Safety requirements make it necessary that a hook assembly maintain its grip on a casting form under all conditions of possible failure of power. The mechanism must be so arranged that the lifting hooks will never tend to open up and drop a casting form in case of power failure. Inasmuch as the hooks are power operated, it becomes important that even in the event of a power failure, the hooks for engaging the flanges of a casting form be prevented from opening while the claws carry the weight of the casting form.

In accordance with the invention a power operated toggle joint is provided for moving the hooks. For most of the range of claw separation, the hook pivot arrangement cooperates with the claw shape so that the weight of the load on the claws reacts upon the hooks to keep them closed. However, the range of claw movement is great enough so that at one end of the range (here the minimum claw separation) the reaction of the load upon the claws creates forces tending to open the claws. This makes for instability and in case of power failure could create dangerous conditions. The toggle arrangement is such that the toggle links are in line (the toggle knee is unbroken) when the unstable hook position is reached. Thus, the toggle itself provides a practically infinite force opposing claw opening forces in the range of instability of the hook and claw positions.

In order that the invention may be fully understood, reference will now be made to the drawings wherein a hook assembly illustrative of the invention is disclosed.

FIGURE 1 is a plan view of a system embodying the present invention.

FIGURE 2 is a section on line 22 of FIGURE 1, the dotted lines showing the hooks at minimum separation.

FIGURE 3 is a side elevation of the assembly illustrated in FIGURE 2 with certain parts broken off.

FIGURE 4 is a view similar to FIGURE 2 but showing the hooks elevated above a concrete slab to permit the vacuum pads to be used.

Referring first to FIGURE 1, casting form 10 having channels 11 and 12 is illustrated. Channels 11 and 12 are each provided with top and bottom flanges 14 and 15 respectively. As has been previously indicated, casting form 10 may have any desired length up to about 50 feet or 60 feet and may have a width in the casting region between about 18 inches .and about 36 inches, depending upon the width of the slabs being cast. It is understood that the width dimensions here are exemplary and, while the invention is limited to a range of widths, the range can be other than given above. The extent of the width range will be determined by the geometry involved in the embodiment of the invention.

As illustrated in the drawing, casting form 10 has casting 17 within it. It is understood that the casting will be stripped from casting form 10 in the manner gene-rally disclosed in the aforementioned patents. As a rule, the stripping is accomplished by having the casting form supported horizontally with the sides extending up. Stripping is accomplished by spreading the casting form sides apart, this generally being accomplished by means engaging bottom flanges 15 of the channels as more fully disclosed in the aforementioned patents. While the invention to be disclosed relates to flangeengaging hook assemblies and may have some application to stripping, the principal field of application of the invention has to do with operating on the casting form or the casting from above the top of the casting form.

The hook assembly forming the subject matter of the present invention cooperates generally with relation to flanges 14 of the channels. It will be observed that, as is usual in such flange structures, the thickness of the flange (the distance between the inside and outside surfaces) decreases as the free edge of the flange is reached. The decrease in flange thickness results in the inside or, in the case of flange 14, the bottom surface of the flange having a slight upward curve beginning from the base of the flange in the web.

Still referring to FIGURE 1, the means for lifting the casting form or slab is an assembly which may be disposed at spaced regions along the length of a casting form. In practice, since dead weight only is to be handled, it is enough to provide lifting assemblies at two spaced regions disposed along the length of a casting form, such spaced regions being conveniently near the ends of a casting form. Inasmuch as the various lifting assemblies are the same, it is only necessaryto describe one in detail. Accordingly, reference will now be made to the remaining figures of the drawing.

A slab and casting form lifting assembly is carried by wide flange I beam 20 having top and bottom flanges 21 and 22 respectively. It is understood that wide flange I beam 20 can be raised, lowered and moved as desired. Bottom flange 22 of the I beam carries vacuum pad 24 having suspension means 25. Means for supporting the weight of a casting slab from beam 20 when pad 24 is exhausted, is provided. No attempt is made to show the details of the vacuum pad or the means for removing air from within the pad to create vacuum conditions permitting the casting to be raised. Such vacuum pads and their suspension means in general are old. It will be observed that is illustrated in FIGURE 2, vacuum pad 24 normally depends from flange 22, the drawing showing the pad in its lowest position.

As has been previously explained in general terms, it is necessary at times to elevate casting form with casting 17 therein. At other times, such as during stripping, it is necessary to elevate casting 17 alone. At still other times, it is necessary to elevate casting form 10 after casting 17 has been removed. Excepting for the time that casting 17 is being removed'from form 10 during stripping, the handling of casting form 10 does not involve suction pad 24 so that the suction pad may be disregarded. It is only when the suction pad is being used for elevating casting 17, that the hook mechanism does not function and must be disposed in a position to be above the slab top face.

Rigidly secured to top flange 21 of wide flange I beam are spaced parallel rigid plates forming a framework. Supported at the top of this framework is air cylinder 31 having top and bottom air inlets 32 and 33. Cylinder 31 is pivotally supported at 34 to permit the cylinder and load to swing sideways without damage to the cylinder. Within cylinder 31 is piston 35 secured to piston rod 36. The air cylinder is of the double acting variety wherein piston 35 may be moved either up or down in the cylinder, depending upon the air conditions existing therein.

Piston rod 36 is secured to toggle pin 38 at the knee of toggle joint links 40 and 41. Toggle joint links 40 and 41 have their free ends coupled to pivot pins 42 and 43 respectively. These pins pass through base portions 44 and 45 of massive hooks 46 and 47. Each hook turns about pin or roller 50 carried by bars 51, welded or otherwise rigidly supported on top flange 21 of the wide flange I beam. Bars 51 have their free ends rigidly secured by blocks 53. Spaced 'bars 51 are disposed on opposite sides of the body of hooks 46 and 47 with pins 50 extending through slots 55 in the bases of the hooks. .The slots in which pins 50 operate are elongated, each slot generally extending straight away from the respective toggle pivot pins 42 and 43. The orientation of slots 55 in hooks 46 and 47 and dimensions of parts are such that piston 35 when fully retracted to its top position in its cylinder will elevate hooks 46 and 47 vertically so that each pivot pin 50 will be near the bottom of its slot 55.

Hook 46 has bottom claw portion 58 extending inwardly toward the opposing claw, the reach of the claws being sufficient to engage the bottom or inner surface of top flange 14. To limit the opening of hooks 46 and 47, stop plates 62 and 63 are provided. These plates are straight bars welded to the bases of the hooks and their location is such that toggle links 40 and 41 are limited to a predetermined maximum angle of toggle joint break. This maximum angle of break determines the maximum separation of claws and hooks. The minimum claw separation occurs when the toggle links extend straight across as shown in dotted outline in FIGURE 2. At this end of the claw moving range, the instability of claw engagement with flanges occurs. In the toggle link arrangement illustrated in dotted outline in FIGURE 2, piston 35 should be at the bottom of its stroke. In the top position of toggle pin 38, this corresponding to the maximum toggle break, piston 35 will be somewhere between the top and bottom ends of cylinder 31 a distance such that hooks 46 and 47 are elevated.

The top part of piston travel in cylinder 31 will be useful for elevating hooks 46 and 47 while the remainder of the piston travel toward the lower end of the cylinder will be useful for moving the hooks and claws toward each other for engagement with the flanges of a casting form. Due to the geometry of the hooks and the lever arms for turning the hooks on the pivot pins, a substantial opening or closing of the hooks is rendered possible with a small movement of the toggle pivot pin.

The dimensions and arrangement of parts and pivots are such that, except when the claw separation is a minimum, the hook assembly is stable and does not tend to open in response to the load on the claws. Where claw engagement at the lower flange surface occurs, a line of action normal to the supporting flange surface can be drawn. So long as the line of action falls outside of the axis of pivot pin 50 (by outside is meant away from companion pivot pin 50) then there will be a moment arm tending to turn a hook toward the companion hook. The load on the two claws of a hook assembly will tend to be stable on the claws and in general will result in forces on the hooks tending to keep the hooks engaged with the flanges. However, when the hooks are handling a narrow slab casting form, the lines of action pass through the pivot points or may even fall between the two opposed pivot points. In such case, the hooks are in unstable condition and the load creates forces on the hooks tending to open them and tending to drop the load.

At this end of the range of claw separation, the piston will be at the bottom of its travel and the toggle links will lie along a straight line. The reaction of the claws tending to open the hooks will be resisted by the toggle links. There will be no component at toggle pin 38 tending to break the toggle joint knee and move piston rod 36 upwardly. It makes no difference whether the cylinder has air in it or not when the hooks are in unstable position. Thus, it will be seen that by proper design, any instability of the hook arrangement due to the narrowness of the casting form will be taken care of by the substantially straight condition of the toggle joint. For most of the range of widths of casting forms to be handled, the condition of the lifting hooks will be such that the weight supported by them will create a component which tends to stabilize the hooks and keep them closed.

Variations may be made in the arrangement of the hook slots and pins 50 as well as the relative location of slots 55 and toggle joint pivot pins 42 and 43.

What is claimed is:

1. A lifting hook assembly for use on casting forms whose widths lie within a substantial range, said assembly comprising a supporting beam, a pair of opposed hooks, each hook having a base portion and an elongated curved body portion terminating in a claw, means supported by said beam for pivotally supporting said hooks at the bases thereof for permitting movement of said hooks so that the distance between opposed claws can be varied, a pair of links pivotally secured to said hooks at regions spaced from the hook pivots, said links extending generally toward each other and having their ends pivotally secured to provide a toggle joint, power means including a rod coupled to said links for operating said toggle joint to control the hook positions, said rod being movable over a range along a line which is substantially normal to a line extending between the centers of the link pivots to provide normal toggle joint action, means for limiting the relative turning movement of a toggle link and hook base portion whereby said toggle joint can break from one end position where said toggle links are along a substantially straight line to another position where the knee of the toggle joint is bent to provide a certain angle, said range of rod movement being substantially greater than is required for operating said toggle joint over its range, said pivotal hook supporting means including means for permitting said hooks to move linear- 1y independently of pivotal motion of hooks about the hook pivots, said linear movement of said hooks being in a direction generally parallel to said rod movement whereby rod movement tending to turn said toggle joint lengths beyond the toggle limits results in movement of said hooks linearly.

2. A lifting hook assembly for use on casting forms whose widths lie within a substantial range, said assembly comprising a supporting beam, a pair of opposed hooks, each hook having a base portion and an elongated curved body portion terminating in a claw, pivot pins supported by said beam, each hook having an elongated slot in the base portion thereof, said pins and slots cooperating for pivotally supporting said hooks, said hooks depending from said pivots and being adapted to be disposed so that the claws will oppose each other, said slots extending generally downwardly, a pair of links pivotally secured at an end of each link to said hooks at the bases thereof at regions spaced from the ends of said slots, means pivotally securing the other ends of said links to provide a toggle joint, power means including a rod pivotally secured to said links at the other ends thereof for operating said toggle joint to control the hook positions, said rod being movable along a vertical line, said toggle joint having a range of movement at one end of which said toggle joint links extend in a substantially straight line and at the other end of which said toggle is broken with said two links having a predetermined angle therebetween, means for limiting the relative turning movement of each toggle link with respect to its hooks to define the limit of toggle joint break, means for defining a range of rod movement between two end positions, one such end position corresponding to said one end position of said toggle joint, the other end position of said rod being beyond the other end position of the toggle joint, the movement of said rod beyond the other end toggle joint position being operable to elevate said hooks with respect to the pivot pins above the normal hook positions.

3. The construction according to claim 2 in combination with additional lifting means disposed between said hooks, said additional lifting means being supported from said beam and having an active operating level which is normally above the normal level of the opposed claws, the hooks being subject to elevation above the level of the added lifting means when said operating rod is in the portion of its travel range beyond the other end toggle joint position.

References Cited by the Examiner UNITED STATES PATENTS 423,548 3/1890 Boyer 294-88 X 3,033,381 5/1962 Noble 294 X OTHER REFERENCES German printed application No. 1,180, 108-Efinder, printed Oct. 22, 1964 (K1. B 66c).

GERALD M. FORLENZA, Primary Examiner.

G. F. ABRAHAM, Assistant Examiner. 

1. A LIFTING HOOK ASSEMBLY FOR USE ON CASTING FORMS WHOSE WIDTHS LIE WITHIN A SUBSTANTIAL RANGE, SAID ASSEMBLY COMPRISING A SUPPORTING BEAM, A PAIR OF OPPOSED HOOKS, EACH HOOK HAVING A BASE PORTION AND AN ELONGATED CURVED BODY PORTION TERMINATING IN A CLAW, MEANS SUPPORTED BY SAID BEAM FOR PIVOTALLY SUPPORTING SAID HOOKS AT THE BASES THEREOF FOR PERMITTING MOVEMENT OF SAID HOOKS SO THAT THE DISTANCE BETWEEN OPPOSED CLAWS CAN BE VARIED, A PAIR OF LINKS PIVOTALLY SECURED TO SAID HOOKS AT REGIONS SPACED FROM THE HOOK PIVOTS, SAID LINKS EXTENDING GENERALLY TOWARD EACH OTHER AND HAVING THEIR ENDS PIVOTALLY SECURED TO PROVIDE A TOGGLE JOINT, POWER MEANS INCLUDING A ROD COUPLED TO SAID LINKS FOR OPERATING SAID TOGGLE JOINT TO CONTROL THE HOOK POSITIONS, SAID ROD BEING MOVABLE OVER A RANGE ALONG A LINE WHICH IS SUBSTANTIALLY NORMAL TO A LINE EXTENDING BETWEEN THE CENTERS OF THE LINK PIVOTS TO PROVIDE NORMAL TOGGLE JOINT ACTION, MEANS FOR LIMITING THE RELATIVE TURNING MOVEMENT OF A TOGGLE LINK AND HOOK BASE PORTION WHEREBY SAID TOGGLE JOINT CAN BREAK FROM ONE END POSITION WHERE SAID TOGGLE LINKS ARE ALONG A SUBSTANTIALLY STRAIGHT LINE TO ANOTHER POSITION WHERE THE KNEE OF THE TOGGLE JOINT IS BENT TO PROVIDE A CERTAIN ANGLE, SAID RANGE OF ROD MOVEMENT BEING SUBSTANTIALLY GREATER THAN IS REQUIRED FOR OPERATING SAID TOGGLE JOINT OVER ITS RANGE, SAID PIVOTAL HOOK SUPPORTING MEANS INCLUDING MEANS FOR PERMITTING SAID HOOKS TO MOVE LINEARLY INDEPENDENTLY OF PIVOTAL MOTION OF HOOKS ABOUT THE HOOK PIVOTS, SAID LINEAR MOVEMENT OF SAID HOOKS BEING IN A DIRECTION GENERALLY PARALLEL TO SAID ROD MOVEMENT WHEREBY ROD MOVEMENT TENDING TO TURN SAID TOGGLE JOINT LENGTHS BEYOND THE TOGGLE LIMITS RESULTS IN MOVEMENT OF SAID HOOKS LINEARLY. 